The present invention relates to a method of constructing a roadway. A roadway in this specification means a highway or other paved surface (e.g. a runway).
Conventional methods for constructing a roadway involve the excavation of large volumes of material, so that a complicated system of supporting strata can be laid and compacted beneath the paved surface, to provide a sufficiently stable foundation.
In regions where the ground is soft, even greater volumes of material must be removed, and replaced by foundation material. To ensure that settlement of the eventual paved surface is not excessive, extensive soil investigations are required before work can proceed.
Where it was necessary to raise the level of the roadway, this has previously been achieved by compacting earth fill or by constructing a multi-span bridge structure onto which was laid a road surface. A common problem with earth filled embankments is to find a suitable source of earth. Often the earth must be transported a considerable distance to the required site. The cost of construction is therefore very high. In addition, the earth fill method requires the imported earth to be properly compacted to the required level and this normally takes a considerable time since the compaction procedure requires the compaction of many individual layers of fill. A further complication is the need to provide culverts to maintain the natural water flow underneath the embankment. Despite these many disadvantages the earth fill method of embankment construction is the most common, since the "bridge" type method of embankment construction is even more expensive.